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Aviation History
1980
1980 - 1133.PDF
FLIGHT International, 5 April 1980 The AFTI/F-16 will have the ability to move independently in the six directions shown here. Manoeuvres in a conventional aircraft are a complex blend of these motions in the auxiliary flight-control com puter which was connected to the existing quadruplex analogue fly-by- wire control system. The latter was retained for safety and to provide autostabilisation and other closed- loop functions. The pilot was provided with a mode selection panel and a CCV controller. This two-axis propor tional force controller replaced the trim switch on the YF-16 sidestick. Input commands were proportional over a +31b force range. Although the flight-control systems differ, both the Fighter CCV and the AFTI/F-16 generate the required aerodynamic forces in the same manner. Direct lift control is a com bination of symmetrical flaperon deflection and balancing tailplane movement. The aircraft is able to climb or descend at constant angles. of attack. Direct sideforce control is" the result of co-ordinated canard and rudder deflection, with wing and tail roll controls counteracting any ten dency for the aircraft to roll. Flat turns, with zero sideslip, are possible. Alternate use of these paired con trol surfaces—wing and tailplane, rudder and canard—can be made to vary angle of attack or sideslip angle independently of the trimmed lift. Pitch and yaw altitude can be varied to point the fuselage to one side of, above, or below a constant flight path. Vertical and lateral translation are a variation on the direct force modes with the surfaces acting to keep air craft attitude constant. It is also possible to blend CCV and conventional flight modes. Direct lift added to conventional longi tudinal control quickens the man oeuvre. Symmetrical flap deflection is commanded by the error between pilot demanded normal acceleration and sensed g. Conversely, a gust is sensed as uncommanded g and the CCV system acts to counteract the disturbance, giving a measure of gust alleviation. Flight-test of the Fighter' CCV showed direct lift and sideforce to be the most powerful modes and also the easiest to use. Simple fuselage pointing tasks were quickly and accurately accomplished. For small position changes—in formation flying for example—vertical translation and direct lift were most useful. For large position changes, over 500ft, direct force modes were preferred for their more rapid response. Automatic manoeuver enhancement provided precise and predictable longitudinal control, reduced pilot workload and improved target tracking. Operationally, the Fighter CCV Combining the flight-control and fire-control systems will allow automatic target tracking and three-dimensional weapons release 1085 Yaw attitude Direct side force Drag modulation Roll attitude Direct lift Pitch attitude testing was divided into air-to-air and air-to-surface evolution. Manoeuvre enhancement was most beneficial to air-to-air tracking, giving quickened response, improved control precision and a smoother ride. Direct force was used for short periods to fine tune aircraft position during target track ing. These latter modes were also used for longer periods during defensive manoeuvring. Fuselage pointing was used in air- to-air tracking, although pilots felt this mode would be more useful if made automatic, such as in inte grated flight and fire control. Useful ness of the translation modes was limited by low translation velocities and slow response. Air-to-air tracking accuracy in a wind-up turn was found to be improved from a basic mean error of 7-0mil to 4-8mil using manoeuvre enhancement and further to 4-lmil using direct force "beep ing." Direct sideforce dominated the BOMBING STRAFING
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